1. Field of the Invention
The present invention relates to a tool for forming a transition from an underground plastic pipe to, for instance, a metallic above ground gas meter riser.
2. Description of the Prior Art
Modern gas utilities have broadly adopted plastic pipe for use with underground natural gas distribution and transmission systems. Consequently, many local and state governmental regulatory agencies have adopted safety codes which require above ground gas meter risers to be constructed of relatively rigid and durable metallic materials which protect against deterioration and external damage of an otherwise plastic riser assembly. Therefore, it is necessary to transition such subterranean plastic pipe to metallic risers for above ground use. It has been common practice to make that transition by means of a riser transition assembly pre-fabricated on a factory assembly line by inserting a length of plastic pipe into a metallic riser elbow and utilizing a completion spigot which expands the wall of the top extremity of the plastic pipe radially outwardly to be compressed by a finishing sleeve of the metallic riser to thereby provide a threaded coupling for attachment to a gas meter or the like.
A spigot and sleeve arrangement, as shown in U.S. Pat. No. 4,293,147 to Metcalfe et al. and licensed to applicant's assignee, has been found satisfactory for forming a spigot and sleeve joint. A factory fabricated transition assembly of this type is shown in U.S. Pat. No. 4,801,159 to SEHORN. While satisfactory for its intended purpose, it would, without a satisfactory tool for completion in the field, have little utility in an application where the spigot and sleeve joint were to be completed in the field. Oftentimes, for a factory assembly line operation, the character of the tool employed to insert the spigot or draw on the finishing sleeve is given little attention, since portability and compactness is of little concern.
As set forth in co-pending patent application Ser. No. 08/163,471, filed concurrent herewith, and assigned to the assignee of the rights in the present invention, there exists a need for a procedure whereby the transition fitting might be conveniently and reliably performed at the installation site by relatively unskilled personnel. The integrity of the final connection depends to a great degree on the ease with which the joint may be completed. Any completion tool, to be practical for use in the efficient and reliable completion of a joint, must be lightweight, compact and convenient for the workmen to use in a foolproof manner to complete a high integrity joint. These requirements are particularly true for field applications where the work must be performed oftentimes in an environment which lacks the comparatively ideal conditions of a factory setting. It is preferable if the same tool can conveniently be employed both to efficiently insert the spigot into the end of the plastic pipe to expand the wall to a flare and then draw the metal riser, including the finishing sleeve, over the expanded flare to form the seal between the riser and the plastic pipe.
Because a great number of such transitions are required in residential and commercial developments, a tool to assemble such transitions efficiently and economically is highly desirable. Due to the high flammability of natural gas, great importance is placed on the resultant integrity of the completed riser assembly and accompanying transition connections to plastic pipe.
It is therefore the object of the present invention to provide a tool, with the attribute for ease of operation, which allows rapid efficient completion of a transition between an above ground metallic gas riser pipe and an underground plastic gas transmission pipe, while producing a transition of high resultant integrity.